Night observation systems are well known in the prior art. The roots of these systems can be traced back to before World War II.
Night observation systems are generally divided into active and passive systems. Some night observation systems work by flooding an area under observation with infrared energy.
Active systems have an infrared filter that uses a special lens coating. When infrared light passes through a filter designed to transmit infrared light below 900 nanometers, the filter glows. An auxiliary source of infrared light can be used to illuminate the object under observation. Objects in the observation area reflect infrared energy back to the sensor in the imaging device. Since the glowing filter is visible and reveals the position of the light source, a disadvantage of these active systems is that the location of a covert observer may be revealed. Other active systems use light sources such as infrared lasers which do not require the concomitant use of a filter.
As technology developed some of the disadvantages of active systems were overcome by the use of passive imaging systems. Passive systems usually do not disclose the location of the observer, since they do not emit visible light. Due to their low resolution, the main disadvantage of these systems is the difficulty encountered in distinguishing the object under observation from background noise, such as infrared energy from other sources. Another example of a problem encountered with low resolution is that, in military situations, during combat maneuvers, camels can be confused for tanks.
There are currently at least two types of passive night vision systems.
One type, known as a thermo-imaging system, picks up the emission of heat energy from the objects under observation. A thermo-imaging system detects long wavelength, for example 8-14 micron, infrared radiation emitted from objects as a result of their temperature, usually -20.degree. to +2500.degree. F. A disadvantage of this type of system is that the resultant image lacks clear, identifying qualities. This is particularly disadvantageous in a law enforcement scenario where a police officer must be able to identify the suspect being imaged in order to maintain a proper chain of custody. With thermo-imaging systems, it is difficult not only to maintain a proper chain of custody but also to distinguish friend from foe. Another disadvantage of the thermo-imaging system is that distortion occurs when the system is exposed to visible or infrared light from, for example, a headlight, a flashlight or the sun. A further disadvantage of the thermo-imaging system is that most systems are designed to be used with an eyepiece for viewing. This decreases the peripheral vision and increases the vulnerability of the observer.
A second type of passive night vision system is called a light intensifier system. A light intensifier system takes a very low level of visible light and magnifies it until it is visible to the naked human eye. Unlike the other described systems, the light intensifier system works in the visible spectrum The light intensifier system does not work in a totally dark environment. Another difficulty with the light intensifier system is that the image produced is green, and usually "grainy" or blurred. Furthermore, distortion occurs when the system is exposed to visible or infrared light from, for example, a headlight, a flashlight or the sun. Light intensifier systems are usually constructed in a binocular or scope configuration which decreases the peripheral vision and increases the vulnerability of the observer.
Thus, both thermo-imaging systems and light intensifier systems have relatively low resolution and create a shadowy image, can be damaged when subjected to high intensity light sources, and may decrease the peripheral vision and increase the vulnerability of the observer.
An example of a hybrid system is that of a light intensifier system with laser illumination. This system uses the traditional, passive, light intensification method of imaging supplemented by an infrared laser light illumination of the field of view. The laser has the capability of "viewing" for great distances. However, the image is usually viewed through an eyepiece and appears green and grainy. Also, compared to the non-coherent light sources used in this invention, the laser does not provide as high a reflective factor or as wide an area of illumination.
With all of the conventional systems, it is difficult to obtain an accurate description of the subject or terrain under observation or to determine if the subject being viewed is holding a weapon.
Also, it is believed that none of the conventional systems accurately determine the distance of an object under observation from the point of observation. As a knowledge of the distance to an object is necessary for the determination of the size of that object, the distance to an object is critical for complete object identification. For example, determining the distance to an object and calculating the size of that object can help distinguish whether the object is an adult or a child.
Night observation systems have been disclosed by Meyers in U.S. Pat. Nos. 4,991,183; 4,853,529; 5,042,048; and 5,056,097. Meyers generally discloses an intensification system that uses laser light to supplement the available unseen light. This illuminates an area through the use of infrared lasers which generate coherent light in the observed area. The object under surveillance is displayed as a green image using an eye piece.
Pinson, in U.S. Pat. No. 4,947,044 for a method and apparatus for covertly viewing a target, disclosed the selection of a frequency band of infrared radiation having the least effective transmittance properties of all frequencies of infrared radiation in given atmospheric conditions to illuminate a target and the detection of the reflection of that selected frequency band of infrared radiation from that target. In Pinson, at sea level, all the bands have wavelengths of greater than 1.35 microns.
Other known systems, such as the one designed by Agema Infra Red Systems, use a thermo-imaging system with a video camera format that is used in surveillance applications as well as the thermo measurement of faults in the inspection of electronic or pressurized systems. Thermo-imaging systems have the disadvantage that the quality of the image decreases as the distance of the object under surveillance from the imaging device increases. It is difficult to determine, in a short time, the accurate distance to the object under observation. As the object under observation moves, it is also difficult to follow that object with precise accuracy.
In U.S. Pat. No. 4,264,927 Raymond et.al. disclose an apparatus for scanning and recording information on railroad cars moving at high speed in order to facilitate the identification of the railroad cars. The apparatus employs a television type camera having a pick-up device with high resolution. In Raymond, the inventors note that an advantage of their system is the avoidance of the need for special labels and devices.
In U.S. patent application Ser. No. 08/517,378, Jones and Lyman introduced an imaging system comprising a non-coherent light source, a filter means, a first imaging means, and a first display means. That application also introduced a range finder having a low power diode, a lens system, a second imaging means, a second display means and a precalibrated scale. Furthermore, that application introduced a movement sensor having a display driver circuit board, a scan threshold detector, a microchip, and a microcontroller.
In the present invention, Jones and Lyman introduce improvements and additional applications to the invention disclosed in U.S. patent application Ser. No. 08/517,378.
An advantage of the invention disclosed in U.S. patent application Ser. No. 08/517,378 is that non-coherent light is fanned out onto the entire field of view. Compared to the relatively small area that is viewed using the Meyers system, this is an advantage, since the whole area that is viewed by the electro-optic imaging sensor can be displayed on a display screen. The present invention uses near infrared wave lengths giving a high degree of reflection off the surfaces under observation. This provides a more accurate gray scale image with the advantage that the display reveals much more detail of the object under observation. An example of the high resolution that is accomplished with the present invention is that if the object under observation is a human being, the observer can determine by looking at the display screen if the human under observation wears glasses, or if he is carrying any weapons, or other objects.
Another advantage of the use of near infrared light in the present invention is the detection and identification of hidden images, codes or marks. Inks, paints or other markings, which reflect light exclusively in the high wavelengths of the visible spectrum or in the near wavelengths of the infrared spectrum are difficult or impossible to detect with the naked eye. Such inks, paints or other markings are often referred to as invisible or transparent. Hidden images or marks can be placed on objects such as, for example, clothing or boxes. One purpose of the use of hidden images, codes or marks is to determine whether an article is genuine or counterfeit. Another reason for using hidden images, codes or marks is to add information without visually cluttering the surface. For example, in shipping a package, each handler may place his or her mark and date stamp on the package without visibly overwriting other information on the package. A further application is in providing additional information to markings such as bar codes. For purposes of this application the term "hidden marks" comprises hidden images, codes and marks.
A further advantage of the use of near infrared light in the present invention is the detection of faults on objects such as, for example, airplane wings and ceramic tiles. The highly reflective properties of near infrared light facilitates the detection of such faults. Surface faults are detected directly. The detection of surface abnormalities is helpful in indirectly detecting faults below the surface. When a surface abnormality is detected other methods may be used to confirm if a true fault exists.
The present invention also provides the advantage that the range or distance of the object under observation is determined with great accuracy. Knowledge of the distance from the object to the viewer is then utilized to determine the actual size of the observed object. Thus, with the current invention, the viewer can determine not only if the object under surveillance is a human being, but also if the human being is an adult or a child.
It is an objective of the present invention to observe objects, including animals and humans, at night, or in any light condition, without emitting visible light and simultaneously to create an image with enough detail to clearly identify the characteristics of the objects under observation. A high resolution image generally allows one to differentiate objects and to distinguish, for example, a human from a weight or structure. If the object is human, it may allow one to determine precise characteristics such as sex, attire and objects that the person is carrying It is another objective of the present invention to enable the user to determine the exact distance from the observation point to the object or objects under surveillance and to estimate the size of the object under observation. Therefore, if the object is human, it may allow one to distinguish an adult from a child. It is another objective of the present invention to create a high resolution image so that small scale movement of the observed object can be detected, without confusing it with other environmental factors. It is another objective of the invention to detect when the observed object makes any significant moves and to distinguish mobile objects from stationary objects. It is another objective of the invention to detect and identify hidden, transparent or "invisible" markings or images on objects. It is also an objective of the invention to detect faults in the surfaces of objects. Other objectives of the invention will be apparent from the specification and claims.
Furthermore, the principles disclosed in this invention can be utilized in conjunction with more conventional systems, such as light intensifier systems and systems employing laser light sources, to improve those systems. A further use of the principles disclosed in this invention is in conjunction with camcorders or video cameras.